Calcium-strontium smoke inhibitors for diesel fuels

ABSTRACT

Oil-soluble organic compounds of strontium and calcium are used in admixture as smoke-suppression additives for diesel fuels. The mixed-metal additives are found to give a greater degree of smoke suppression than would be expected, based on the effectiveness of either metal alone.

United States Patent 1191 Skinner Nov. 19, W74

[ CALCKUM-STRONTIUM SMOKE 3,389,978 6/1968 Mann et al 44/57 INHIBITORS FOR DIESEL FUELS [75] Inventor: Davis A. Skinner, Fullerton, Calif. 3:437:4 5 4 19 9 [73] Assignee: Union Oil Company of California, Los Angeles, 3,644,106 2/1972 Burnop 44/51 [22] Filed: July 3, 1972 [2i] Appl. N0.: 268,774 Primary Examiner-Daniel E. Wyman Assistant Examiner-Mrs. Y. H. Smith Related U.S. Application Data 4 Attor e A m, or Fzrm-Lannas S. Henderson, [63] Continuation-impart of Ser, No. 88,885, Nov. 12, Ri hg gc }i D S did 1970, abandoned, which is a continuation-in-part of Ser. No. 740,809, May 31, 1968, abandoned.

52 [1.8. Ci 44/70, 44/57, 44/78, [57] ABSTRACT l t (3 1%: Oil-soluble organic compounds of strontium and cal- [58] d 70 cium are used in admixture as smoke-suppression ad- 0 an 1 ditives for diesel fuels. The mixed-metal additives are found to give a greater degree of smoke suppression than would be expected based on the effectiveness of [56] References Cited 4 either metal alone. UNITED STATES PATENTS I 3,085,866 4/1963 Gay et al. 44/57 7 Claims, 1 Drawing Figure CALCIUM-STRONTIUM SMOKE INHIBITORS OR DIESEL FUELS RELATED APPLICATIONS BACKGROUND AND SUMMARKOFJNVENTKLN' A great many oil-soluble organometallic compounds have been suggested and/or used as smoke suppressants in diesel fuels. In recent years the most widely used additives have been based on barium compounds, in amounts providing about 2.6 5.3 grams of barium metal per gallon of fuel. However, evidence appears to ,be accumulating that the barium compounds discharged into the atmosphere from diesel powered vehicles using such fuels may constitute as much a health hazard as the smoke contaminants which they suppress. (Chem. Eng. News, May 22, 1972 p. 17). It has accordingly become desirable, and may become essential, to develop effective and economical substitutes for barium in smoke suppressant additives.

l have now discovered that certain combinations of oil-soluble calcium and strontium compounds are not only more effective than barium compounds for smoke reduction (on the basis of equal metal weights), but that the Ca-Sr combinations are synergistic in that they give a higher degree of smoke reduction than equal weights of calcium or strontium alone. Moreover, although Ca-Ba combinations have also been found to be synergistic in reference to either component alone, the Ca-Sr combinations give synergistic results which exceed the synergistic results achieved with corresponding (a-Ba combinations. This is aptly illustrated by the graphs in the attached drawing, which depict data from Examples 1 and 2 herein, to be explained in more detail hereinafter. As a result of these discoveries, the barium in conventional additives can now be replaced with smaller overall proportions of calcium and strontium compounds to achieve the same degree of smoke relduction, while at the same time avoiding the emission iof toxic metal compounds into the atmosphere.

% DETAILED DESCRIPTION i The invention contemplates the use herein of any oil-- lsoluble hydrocarbon sulfonate, naphthenate or phenate ;of calcium in admixture with any desired oil-soluble hydrocarbon sulfonate, naphthenate or phenate of strontium. The preferred compounds are the so-called overbased" salts, in which the atomic ratio of calcium or strontium to acidic hydrogen atoms in the organic moiety is greater than 1%, preferably between about 1.3/2 and 2/2. For adequate oil-solubility the sulfonate, naphthenate or phenate radical should comprise a hy-. drocarbon grouping containing at least about 10, pref- I 60 erably about 12-30 carbon atoms.

Suitable sulfonates include the salts (calcium or strontium) alkylsulfonic acids, arylsulfonic acids and alkylaryl sulfonic acids. Preferred sulfonates comprise the salts of petroleum sulfonic acids such as are commonly obtained by the treatment of aromatic mineral oil fractions with sulfuric acid or SO;,. Suitable naphthenates can be obtained by reacting Ca(OH) or Sr(OH) with naphthenic acids derived from petroleum or other sources. The useful petroleum-derived acids are principally those removed from the lubricating oil and gas oil fractions of petroleum which boil within the range from about 500F to about 1000F. at atmospheric pressures. These acids normally contain from about 8 to about 30 carbon atoms per molecule and distill in the range of from about 250F. to about 600F. at 2 mm. of mercury absolute pressure. Such acids can range in saponification value from about 50 to about 300 mgs of KOl-I per gram on an unsaponifiables-free basis.

Suitable phenates can be obtained by reacting Ca- (OH) or Sr(OH) with suitable alkylated phenols such as hexylphenol, heptylphenol, dodecylphenol, dihexylphenol, diisopropylphenol, tributylphenol, didodecylphenol, octadecylphenol, dioctyllphenol, polypropene (molecular weight of l50)--substituted phenol, 'polyisobutene (molecular weight of 350)-substituted phenol, cyclohexylphenol, dodecyl cyclohexylphenol, and the like.

, Suitable exemplary sulfonates, phenates and naphthenates for use herein, and methods for their prepara- .tion, are described in more detail in US. Pat. Nos. 3,410,670, 3,415,632 and 3,389,978.

A preferred group of salts for use herein comprises i the naphthenates described above. These materials appear to be advantageous in that they do not promote water emulsification into the fuel to as great an extent as do some of the sulfonates for example.

Although synergism appears evident in all finite concentrations of the metals in the fuel, the combined total weight of the two metals is preferably between about 0.5 and 3 gms per gallon, and still more preferably between about 1 and 2.8 gms/gal. The preferred weightratios of Ca/Sr are between about H9 and 9/ l, and still more preferably between about 2/8 and. 6/4.

The term diesel fuel" as employed herein is intended to include any mineral oil fraction boiling substantially within the range of about 250 to 850F. This includes narrower boiling fractions which could be used as diesel fuels, but are more commonly used as turbine fuels or jet fuels.

The following examples are cited to illustrate the invention, but are not to be construed as limiting in scope:

EXAMPLE 1 illustrated by the top graph in the attached drawing.

The strontium additive was a sulfonate prepared by re- J acting strontium chloride with the sodium salt of a sull fonated lube oil stock having an average molecular iweight of about 350-400, the final product containing ;2.8 weight-percent Sr and 2.6 percent S. The calcium ladditive was a superbased phenate of a polyisobutenyl phenol having an average molecular weight in the 1 range of about 450-500, and containing 9 weightpercent Ca. The combined additive level of Ca plus Sr 5 was fixed at 2.575 gms/gallon of fuel (a number 2 diesel fuel).

The fuel-additive mixtures were tested in a Cummins NHC-4 diesel engine, with the exhaust therefrom being 7 monitored in a Hartridgesmoke meter. T he engine was operated withaloadbf about 234 pounds, at an RPM. of 2010, the brake horsepower being about 117.5, or 3 about percent of the rated load capacity. As depicted in the drawing the results were as follows:

Table 1 EXAMPLE 3 M t I R t, Another strontium additive was prepared by reacting e a :1 l in Additive Percent Reduction in Sr(( )H) with a petroleum naphthemc acid m xture Mixture, wz-% Smoke Reading having an acid number of 230 mg KOH/gm, to yield a C S 5 naphthenate containing 3.5 weight-percent Sr. This ad- 8 6 (Base Fuel) 0 ditive was found to exhibit smoke suppressing activity I00 0 71.5 substantially identical to that of the strontium sulfonate 28 28 g additiye of Example 1, but exhibited superior water- 0 100 305 emulsion resistance by a routine laboratory deemulsil0 bility test method, as indicated by the following data:

m V Tab1e 3 "WWW fi'h Break Additive g.Sr Timc,"" lnterfacc Oil C1arity"" in Fuel pcr Gal. Minutes Rating Mins 16 Hr Sr Petrosulfonutc 1.27 9.5 5 5 5 Sr Naphthcnate 1.38 1.9 4 3 2.5 None 0 2.6 3 2.5 1.5

"" Minutes to separate into two phases. Scale: I (clean interface) to 5-(emulsion at interface). Scale: 1 (clear) to 5 (very cloudy).

The broken line in the attached drawing indicates the expected smoke reduction of the mixed additives, based on the activity of either additive alone. It will be seen that at the 60% Sr level, the expected smoke reduction would be about 77 percent, whereas the actuation reduction was 85 percent. It is thus evident that a substantial synergistic effect is obtained by using the mixed Ca-Sr additives.

EXAMPLE 2 The lower curve in the attached drawing depicts the results obtained when the strontium additive of Example l was replaced by metal-equivalent proportions of a barium phenate containing 22 weight-percent Ba, and wherein the phenate radical was a polyisobutenyl phenol having an average molecular weight in the range of about 450-500. As depicted, the results, (under the same test conditions) were as follows:

m. 1... a arent 515135-65 mana ers;are;

synergism, but that the peak effect is about 7.5 percentage points below the peak synergistic point on the Sr-Ca curve.

From the foregoing, it will be apparent that the present invention provides a means for eliminating the use of barium in diesel fuels, while at the same time reducing the overall amount of metals required for a given degree of smoke reduction. The following claims are believed to define the true scope of the invention:

1 claim:

1. A smoke suppressant for diesel fuels comprising a mixture of an oil-soluble hydrocarbon sulfonate, naphthenate or phenate of calcium and an oil-soluble hydrocarbon sulfonate, naphthenate or phenate of strontium, the metal content of the mixture comprising about 10-90 weight-percent calcium and about 90-10 weight-percent of strontium.

2. A smoke suppressant as defined in claim 1 wherein the metal content thereof comprises about 20-60 weight-percent calcium and about -40 weightpercent strontium.

3. A smoke suppressant as defined in claim 1 wherein said sulfonate, naphthenate and phenate radicals comprise a hydrocarbon grouping containing 12-30 carbon atoms.

4. A diesel fuel containing admixed therein a smokesuppressant additive, said additive comprising a mixture of an oil-soluble hydrocarbon sulfonate, naphthenate or phenate of calcium and an oil-soluble hydrocarbon sulfonate, naphthenate or phenate of strontium, the metal content of the mixture comprising about 10-90 weight-percent calcium and about -10 weight-percent of strontium.

5. A diesel fuel as defined in claim 4 wherein the metal content of said additive comprises about 20-60 weight-percent calcium and about 80-40 weightpercent strontium.

6. A diesel fuel as defined in claim 4 wherein sufficient of said additive is employed to provide in the fuel a combined concentration of calcium and strontium of between about 0.5 and 3 gms per gallon.

7. A diesel fuel as defined in claim 4 wherein said sulfonate, naphthenate and phenate radicals comprise a hydrocarbon grouping containing 12-30 carbon atoms. 

1. A SMOKE SUPPRESSANT FOR DIESEL FUELS COMPRISING A MIXTURE OF AN OIL-SOLUBLE HYDROCARBON SULFONATE, NAPHTHENATE OR PHENTE OF CALCIUM AND AN OIL-SOLUBLE HYDROCARBON SULFONATE, NAPHTHENATE OR PHENATE OF STRONTIUM, THE METAL CONTENT OF THE MIXTURE COMPRISING ABOUT 10-90 WEIGHT-PERCENT CALCIUM AND ABOUT 90-10 WEIGHT-PERCENT OF STRONTIUM.
 2. A smoke suppressant as defined in claim 1 wherein the metal content thereof comprises about 20-60 weight-percent calcium and about 80-40 weight-percent strontium.
 3. A smoke suppressant as defined in claim 1 wherein said sulfonate, naphthenate and phenate radicals comprise a hydrocarbon grouping containing 12-30 carbon atoms.
 4. A Diesel fuel containing admixed therein a smoke-suppressant additive, said additive comprising a mixture of an oil-soluble hydrocarbon sulfonate, naphthenate or phenate of calcium and an oil-soluble hydrocarbon sulfonate, naphthenate or phenate of strontium, the metal content of the mixture comprising about 10-90 weight-percent calcium and about 90-10 weight-percent of strontium.
 5. A diesel fuel as defined in claim 4 wherein the metal content of said additive comprises about 20-60 weight-percent calcium and about 80-40 weight-percent strontium.
 6. A diesel fuel as defined in claim 4 wherein sufficient of said additive is employed to provide in the fuel a combined concentration of calcium and strontium of between about 0.5 and 3 gms per gallon.
 7. A diesel fuel as defined in claim 4 wherein said sulfonate, naphthenate and phenate radicals comprise a hydrocarbon grouping containing 12-30 carbon atoms. 